<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
        <title></title>
        <!--
            vw: 占屏幕宽度的X%
            vh: 占屏幕高度的X%
            100vw -> 铺满整个屏幕宽度
            100vh -> 铺满整个屏幕高度
            大小设置统一用vw
        -->
        <style>
            body {
                margin: 0;
                padding: 0;
            }
        </style>
	</head>
	<body>
        <div style="width: 50vw; height: 100vh;background-color: #f88; display: flex; justify-content: center; align-items: center;">
            <span style="font-size: 5vw;">今天天气热死了</span>
        </div>
	</body>
</html>